Gethin Jenkins accepts he may have to miss next summer's British and Irish Lions tour of Australia if Toulon reach the French Top 14 final.
Jenkins knew the potential ramifications when he signed for Toulon last summer and Press Association Sport understands his loyalty in any tug-of-war would be with the club.
The Lions open their 10-match tour against the Barbarians in Hong Kong on June 1 - the same day as the Top 14 final - but Jenkins does not have a release clause in his contract and Toulon have confirmed through coach Bernard Laporte that they would not be releasing any potential Lions early.
Laporte outlined his hard-line stance ahead of a scheduled meeting with Gatland, who has flown to France specifically to discuss the thorny issue of player release.
"The international window begins on the weekend of June 9. Everything that happens before that is outside of the window," Laporte told L'Equipe. "As far as freeing up Gethin, in principle, it's a no. If he plays in the final, he will leave the day after, on Sunday June 2, but not before.
"You don't pay a player to be playing with the Lions at the most important moment of the season."
On the day he was confirmed as head coach, Gatland highlighted how Nathan Hines had walked out on Perpignan before the 2009 Top 14 final in order to tour with the Lions. But Hines was leaving Perpignan anyway that summer.
With Laporte adamant and Jenkins tied to the terms of his deal, Gatland will have to cross his fingers that Toulon do not reach the final.
If they do, the Lions coach would have to soften his stance if he is to have one of the world's leading loosehead props available for the Test series against Australia.
"You don't want to cut your nose off to spite your face in terms of making those players unavailable if they're really, really important for you," Gatland said on Tuesday. "But I'm also really, really conscious that you want the whole squad together. You don't want people coming out late on a Lions tour - you want them in right from the start."